Many laboratories including those involved in life science research often carry out multiple reactions simultaneously, for example, using reaction plates having multiple reaction vessels such as 24, 48, 96, or 386 wells. Carrying out reactions in plates can facilitate automation of laboratory processes. Many lab instruments are now adapted to receive multi-well plates for various operations such as heating and cooling and centrifugation.
In some cases, it is useful to be able to optically interrogate a set of samples while they are within the multi-well plate without having to transfer the samples to a separate optical instrument. It can be desirable to carry out reactions such as polymerase chain reaction (PCR), which require heating and cooling, and measure the extent of such reactions optically while the reaction is carried out without removing the samples from the plates, and without removing the plate from the heating and cooling system.
The advent of Polymerase Chain Reaction (PCR) in 1983 has revolutionized molecular biology through vastly extending the capability to identify, manipulate, and reproduce genetic materials such as DNA. Now, PCR is routinely practiced in medical and biological research laboratories for a variety of tasks, such as the detection of hereditary diseases, the identification of genetic fingerprints, the diagnosis of infectious diseases, the cloning of genes, paternity testing, and DNA computing. The method has been automated through the use of thermal stable DNA polymerases and machines capable of heating and cooling genetic samples rapidly, commonly known as thermal cyclers.
The optical measurements useful for interrogating these reactions can involve the measurement of fluorescence. To measure fluorescence, excitation light is directed at the samples in the sample vessels, and light emitted from the fluorophores in the samples is detected. It is often desirable that the transfer of light from the light source to the wells be carried out effectively and efficiently. Optical systems for directing light to sample plates is known, for example, as described in U.S. Pat. Nos. 6,942,837, 7,369,227, 6,852,986, and 7,410,793. While optical systems for directing light to sample vessels in plates and detecting light from the sample vessels are known. There is a need for optical systems which can so more effectively and efficiently.